Some advice Greg hasn't gotten yet:
With a 4WD tractor, turn off the 4WD when it isn't needed (e.g. not using the FEL, ground is dry, and especially when travelling on pavement). This will save a lot of tread on the front tires, to have them free-wheeling.
My normal state for 4WD is OFF in the Summer, unless using the FEL, and ON in the Winter, unless driving on pavement.